1. Technical Field
The present disclosure relates to a portable transceiver communicating with a vehicle control system, more specifically, to a portable transceiver communicating with a vehicle control system and including a vehicle locator feature.
2. Discussion of the Related Art
A remote transmitter is typically used in conjunction with a remote keyless entry (RKE) system to allow a user to lock and unlock vehicle doors, trunks, control alarm systems, or activate vehicle features such as remote start, without the need to use a key. A remote transmitter typically includes a small handheld transmitter housing that can be mounted to a user's key chain. One or more small buttons are located on the housing to allow the user to send desired control signals to a receiver in a vehicle.
As RKE systems have become integrated with vehicle control systems, remote transmitters used therewith have been designed to handle additional non-RKE functions, such as arming/disarming alarms or remote start of the vehicle's engine, etc. As a result, such remote transmitters include additional switches or buttons while retaining the convenient small size of their predecessors. This, however, has led to remote transmitters having a multitude of finger-operated buttons thus complicating the operation thereof.
In an effort to reduce the proliferation of keys on remote transmitters, remote transmitters have been designed to include a user interface, such as a display, in combination with a small number of buttons.
In addition to the one-way communication between remote transmitters and vehicle control systems, remote transceivers have been developed for bi-directional communication. In particular, remote transceivers are capable of communicating with vehicle control or security systems while at the same time are able to receive status information associated with such systems.
Forgetting where a vehicle is parked can be a serious problem in large parking lots such as in shopping malls, multi-level parking lots, and the like.
Global Positioning System (GPS) devices are examples of a radio-based technology that provides direction and distance information to a pre-determined starting point (waypoint), and display this information on a display screen, for example.
GPS is a world-wide radio navigation system formed by a group of 24 satellites and their associated ground stations. GPS uses these satellites, appropriately called NAVSTAR (Navigation Satellite Timing and Ranging), to calculate ground positions. The basis of GPS operation is the use of triangulation from the satellites. To triangulate, a GPS receiver measures distance using the travel time of radio signals. However, to measure travel time, GPS needs very accurate timing, plus it needs to know exactly where the satellites are in space. To solve this problem, each of the 24 satellites is inserted into a high enough orbit (12,000 miles) to preclude interference from other objects, both man-made and natural, and to insure overlapping coverage on the ground so that a GPS receiver can always receive from at least four of them at any given time. In addition, compensation is inserted for any delay the signal experiences as it travels through the atmosphere to the receiver.
With the satellites operating at 12,000 miles above the earth's surface, they are arranged in strategic positions and orbit the earth every 12 hours. Each satellite transmits a low-power radio signal in the UHF frequency range; the frequencies used are designated as L1, L2, and so forth. GPS receivers listen on the L1 frequency of 1575.42 MHZ. This signal, since it is line-of-sight, will reach the ground receiver unless it is obstructed by solid objects, such as buildings and mountains.
The L1 signal is accompanied by a pair of pseudo-random signals (referred to as pseudo-random code) which is unique to each satellite. These codes are identified by the GPS receiver and allow for the calculation of the travel time from the satellite to the ground. If this travel time is multiplied by the speed of light, the result is the satellite range (distance from satellite to receiver). The navigation information provided by each satellite consists of orbital and clock data, plus delay information based on an ionospheric model. Signal timing is provided by highly accurate atomic clocks. The GPS receiver uses NAVSTAR satellite signals as a way of determining exact position on earth.
GPS receivers are intended for navigational use, wherein the calculated latitude and longitude location is displayed on some form of geographic or topographical map. These GPS receivers may be used to locate a vehicle but they can be bulky and require the user to carry them around along with their RKE system. Further, the user has to remember to activate the GPS receiver to set the waypoint of a parked vehicle, for example.